Embodiments in accordance with the present invention relate to a disk storage device being typical of a magnetic disk device and, more specifically, to a technology of precluding erroneous writing as a result of influence by vibration caused by thermal distortion of components configuring the disk storage device.
In a magnetic disk device configured by a plurality of components each having a different thermal expansion coefficient, the difference of the thermal expansion coefficients among the components causes stress, i.e., thermal distortion, to a junction portion of the components. If the stress by the thermal distortion is concentrated at specific portions, this results in vibration called “chatter vibration” or “stick-slip”. It is known that the stick-slip resulted from the thermal distortion easily occurs with a rapid temperature change exceeding a fixed temperature gradient. The temperature gradient here means the amount of temperature change per unit time. Because the magnetic disk device has been recently packed with much higher density for recording, even with a slight stick-slip, the recording head resultantly vibrates and thus an off-track write is generated. There is thus a problem of causing corruption of data recorded in any adjacent tracks.
[Patent Document 1] JP-A-6-325508
[Patent Document 2] JP-A-2003-297025
[Patent Document 3] JP-A-10-199120
With an object of reducing the thermal distortion resulting from difference of the thermal expansion coefficients among the constituent components, for example, Patent Document 1 describes the technology of providing a carriage high in reliability by reducing the thermal expansion coefficient of a carriage made of magnesium alloy for use for a magnetic disk device, and by reducing the thermal stress and the thermal distortion caused by the difference of thermal expansion coefficient from other material for combination use.
The technology described in Patent Document 1 actually offers effects of decreasing the thermal distortion. With a highly-packed magnetic disk device for recording, however, there are possibilities of causing corruption of recording data even with a slight stick-slip, and having a difficulty of completely preventing the stick-slip from occurring due to the thermal distortion because the magnetic disk device is configured by a plurality of components. There thus remains a possibility of causing corruption of recording data due to stick-slip.
On the other hand, various many patent applications have been so far filed about the technology for a disk storage device being typical of a magnetic disk device, aiming to protect the recording data and increase the device reliability irrespective of the temperature environment. For example, Patent Document 2 describes the technology of, with a temperature sensor provided for detecting the temperature inside of the disk device, changing the manner of a writing process depending on whether the temperature is within a range of operation guarantee temperature for a magnetic disk device. More in detail, when the temperature of a magnetic disk device does not fall in the range of the operation guarantee temperature, verification is made after writing to a disk to see whether the writing was made in a normal manner. When any error is found by such verification, the writing is retried again, and after the retry is made for a predetermined number of times, the writing process is prohibited.
Patent Document 3 describes, for the purpose of preventing the access time from being lengthened, detecting the temperature in the surrounding environment of a magnetic disk device (hereinafter, referred to as environment temperature), and when the temperature is equal to or higher than a fixed value, stopping the long seek operation, reducing the transfer rate for a signal processing IC, and when the temperature is equal to or higher than a fixed value, prohibiting the writing operation. Patent Document 3 also describes estimating the temperature that is expected to be reached after a minute based on a past record about the temperature change, and based thereon, exercising control over fans and heaters in a close range, and exercising control over the magnetic disk device. More in detail, when the temperature is predicted to be high, control is exercised over the magnetic disk device and the fans, and when the temperature is predicted to be low, control is exercised over the heaters. Note here that the specific details of the control application over the magnetic disk device with the high temperature prediction are similar to those of the control application with the high temperature detection, e.g., writing prohibition, prohibition of the long-seek operation, and others.
With the disk storage device configured by a plurality of components each having a different thermal expansion coefficient, however, even when the temperature is within a range of the operation guarantee temperature for the device, the stick-skip occurs if the temperature rapidly changes, i.e., greater than a fixed temperature gradient. The technologies described in Patent Documents 2 and 3 are both those of detecting the compensation temperature for the operation of the magnetic disk device, and no consideration is given to the stick-slip caused by the thermal distortion. Therefore, no means is described therein for preventing an off-track write as a result of stick-slip.
As such, with the previous technologies described in Patent Documents 2 and 3 for detecting the operation guarantee temperature for a magnetic disk device, it is impossible to effectively prevent generation of an off-track write caused by stick-slip.
As described in the foregoing, with a disk storage device configured by a plurality of components each having a different thermal expansion coefficient, even when the temperature is within a range of the operation guarantee temperature for the device, stick-skip occurs due to thermal distortion if the temperature rapidly changes, i.e., greater than a fixed temperature gradient, thereby easily resulting in corruption of recording data by the off-track write.
The present invention is proposed in consideration of the problems described above, and an object thereof is to provide a disk storage device and a control method for the disk storage device, which are capable of preventing an off-track write caused by a stick-slip resulted from thermal distortion.